WindowsImpersonationContext Class
Represents the Windows user prior to an impersonation operation.
Assembly: mscorlib (in mscorlib.dll)
The WindowsImpersonationContext type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | Dispose() | Releases all resources used by the WindowsImpersonationContext. |
![]() | Dispose(Boolean) | Releases the unmanaged resources used by the WindowsImpersonationContext and optionally releases the managed resources. |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
![]() | Undo | Reverts the user context to the Windows user represented by this object. |
The following example demonstrates how to impersonate a user and then revert to the original identity.
// This sample demonstrates the use of the WindowsIdentity class to impersonate a user. // IMPORTANT NOTES: // This sample requests the user to enter a password on the console screen. // Because the console window does not support methods allowing the password to be masked, // it will be visible to anyone viewing the screen. // On Windows Vista and later this sample must be run as an administrator. using System; using System.Runtime.InteropServices; using System.Security.Principal; using System.Security.Permissions; using Microsoft.Win32.SafeHandles; using System.Runtime.ConstrainedExecution; using System.Security; public class ImpersonationDemo { [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)] public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken); [DllImport("kernel32.dll", CharSet = CharSet.Auto)] public extern static bool CloseHandle(IntPtr handle); // Test harness. // If you incorporate this code into a DLL, be sure to demand FullTrust. [PermissionSetAttribute(SecurityAction.Demand, Name = "FullTrust")] public static void Main(string[] args) { SafeTokenHandle safeTokenHandle; try { string userName, domainName; // Get the user token for the specified user, domain, and password using the // unmanaged LogonUser method. // The local machine name can be used for the domain name to impersonate a user on this machine. Console.Write("Enter the name of the domain on which to log on: "); domainName = Console.ReadLine(); Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName); userName = Console.ReadLine(); Console.Write("Enter the password for {0}: ", userName); const int LOGON32_PROVIDER_DEFAULT = 0; //This parameter causes LogonUser to create a primary token. const int LOGON32_LOGON_INTERACTIVE = 2; // Call LogonUser to obtain a handle to an access token. bool returnValue = LogonUser(userName, domainName, Console.ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, out safeTokenHandle); Console.WriteLine("LogonUser called."); if (false == returnValue) { int ret = Marshal.GetLastWin32Error(); Console.WriteLine("LogonUser failed with error code : {0}", ret); throw new System.ComponentModel.Win32Exception(ret); } using (safeTokenHandle) { Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No")); Console.WriteLine("Value of Windows NT token: " + safeTokenHandle); // Check the identity. Console.WriteLine("Before impersonation: " + WindowsIdentity.GetCurrent().Name); // Use the token handle returned by LogonUser. using (WindowsIdentity newId = new WindowsIdentity(safeTokenHandle.DangerousGetHandle())) { using (WindowsImpersonationContext impersonatedUser = newId.Impersonate()) { // Check the identity. Console.WriteLine("After impersonation: " + WindowsIdentity.GetCurrent().Name); } } // Releasing the context object stops the impersonation // Check the identity. Console.WriteLine("After closing the context: " + WindowsIdentity.GetCurrent().Name); } } catch (Exception ex) { Console.WriteLine("Exception occurred. " + ex.Message); } } } public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid { private SafeTokenHandle() : base(true) { } [DllImport("kernel32.dll")] [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] [SuppressUnmanagedCodeSecurity] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool CloseHandle(IntPtr handle); protected override bool ReleaseHandle() { return CloseHandle(handle); } }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

